DESCRIPTION (Applicant's abstract): Respiratory epithelial cells are active participants in the host response to the initial stages of bacterial infection. Mutations in CFTR may affect the immunological function of the airway epithelium. Normal mucociliary clearance mechanisms usually prevent transiently inhaled bacteria from coming in contact with the epithelial cell. In cystic fibrosis (CF) occasional bacteria, particularly Pseudomonas aeruginosa elude the normal defenses and are able to bind to asialylated glycolipids found in increased numbers on the surface of CF epithelial cells. Binding to these receptors triggers the epithelial cell to produce large amounts of proinflammatory cytokines, particularly interleukin-8, a major chemokine for polymorphonuclear leukocytes. Neutrophil dominated airway inflammation is a predominant finding in CF. In the studies proposed the epithelial signaling pathway activated by adherence of bacteria to ceramide-associated membrane components, resulting in the activation of NF-kappa-B and IL-8 transcription will be defined. S. aureus, another pathogen in CF, recognizes the same asialylated glycolipid receptors as do P. aeruginosa, suggesting that this gram positive organism can stimulate the same signaling pathway to induce epithelial IL-8 production. We will determine if both species elicit similar epithelial inflammatory response. In addition to the exogenous stimulus for NF-kappa-B activation provided by P. aeruginosa and S. aureus, CF epithelia may be also endogenously stimulated to activate NF-kappa-B. The accumulation of misfolded proteins in the endoplasmic reticulum, the fate of much mutant CFTR, is known to generate active NF-kappa-B acting by a Ca2+-responsive pathway. Experiments are described to determine if endogenous NF-kappa-B activation is a direct consequence of CFTR mutations and resultant abnormal protein trafficking, and if so, how this pathway is regulated. These studies should reveal the different cellular signaling mechanisms which are activated in the CF epithelium and suggest new targets for the modulation of the excessive epithelial inflammatory response which ultimately destroys the CF lung, but is ineffective in clearing infecting organisms.